Knee braces are utilized to provide additional support to the knee wherein such support is desirous because of knee instability due to surgery, deformity, or the like, and knee braces are also commonly employed by athletes to protect against injury or provide additional support to a weakened knee joint. Knee braces may merely consist of an elastic sheath surrounding the knee, or the brace may be of a complicated nature utilizing a plurality of structural elements engaging the leg at the knee, and providing support above and below the knee joint.
In those knee braces of relatively complex construction for providing maximum knee support, it is known to engage the knee adjacent the joint utilizing hinge elements at the lateral portions of the knee and employ leg embracing collars or cuffs at the thigh and shin associated with the hinge wherein relative pivoting of the hinge arms is controlled to limit flexing and extension of the leg at the knee joint. A typical example of such apparatus is shown in U.S. Pat. No. 4,372,298.
Knee braces of the aforementioned type have the common deficiency of not maintaining the desired position on the leg. The knee brace will tend to "ride up" or "drop" relative to the knee causing the hinge to be misaligned to the knee and reducing the effectiveness of the brace, and in extreme instances, rendering the brace ineffective and a hindrance to limb movement.
Also, polycentric hinges used with knee braces having stop structure for regulating and limiting the extent of pivoting of the hinge arms or hinge elements have difficulty in maintaining the original adjustment controlling the degree of hinge movement which regulates flexing and extension. Relatively high forces are imposed upon the hinge arms during use and stops utilizing friction for positioning are ineffective to maintain the desired adjustment over extended periods of time and the stop structure of known non-friction stop hinges such as shown in U.S. Pat. No. 4,599,998 will not maintain the original setting.
It is an object of the invention to provide a knee brace which utilizes a flexible cage tightly strapped to the knee in such a manner that the cage is firmly and accurately positioned to the knee and will not shift relative to the knee during use.
A further object of the invention is to provide a knee brace having a flexible knee cage accurately positionable and maintainable with respect to the knee and wherein the brace includes upper and lower leg embracing cuffs which are suspended from the cage and utilize the permanent positioning of the cage to determine and maintain their position with respect to the associated portion of the leg.
Yet a further object of the invention is to provide a knee brace having upper and lower leg embracing members which are suspended from a flexible knee cage encompassing the knee and positioned thereto wherein straps tightening the flexible knee cage to the knee are also attached to the leg members in such a manner as to improve stability of the brace upon the leg without significantly interfering with leg movement and bending of the knee joint.
Additionally, an object of the invention is to provide a knee brace having a polycentric hinge located at each lateral portion of the knee, the hinge utilizing arms pivotally related to each other and including range of pivotal motion limiting structure having adjustable stops wherein the original positioning of the stops is accurately maintained over extended periods of time and will not be inadvertently changed due to the normal forces applied thereto during use.
Yet another object of the invention is to provide hinge structure for a knee brace having a body upon which the inner ends of hinge arms are pivotally mounted, gear teeth being defined upon the arms' inner ends concentric to the associated arm pivot axis, and a displaceable gear rack being located between the arms' inner ends meshing with the arms' gear teeth thereby interconnecting the arms to produce simultaneous pivotal movement. Adjustable stops in the form of screws are threaded into the body in alignment with the ends of the rack and the rack movement wherein a positive abutment between the rack and adjustment screws takes place to limit arm pivoting and the angular relationship of the hinge arms may be accurately controlled and maintained.
In the practice of the invention a flexible knee cage encompasses the anterior and lateral portions of the knee. The knee cage is formed of a flexible resilient material and includes a central opening receiving the patella. The upper front portion of the cage includes a reinforced area which wraps about the superior edge of the knee and the lateral cage portions are provided with condyle pads located inwardly of the hinges that are affixed thereto. Inelastic straps are attached to the upper and lower lateral portions of the knee cage for pulling the knee cage snugly into engagement with the knee.
A limited range of motion hinge is affixed to each lateral portion of the cage exteriorly of the lateral condyle pads. The hinge includes upwardly and downwardly extending arms, and the arms include inner ends separately pivotally connected to the hinge body forming a polycentric arrangement. The arms' inner ends are formed with gear teeth concentric with the associated arm pivot and a gear rack interposed between the arms meshes with the gear teeth and is guided for linear displacement as the arms pivot. Adjustable stops affixed to the hinge body in alignment with the ends of the rack engage the rack ends to limit the rack movement as the arms pivot to regulate the relative extent of arm pivoting.
An upper relatively rigid cuff of a U-configuration is mounted upon the outer ends of the upper hinge arms, and a lower cuff of U-configuration is similarly attached to the outer ends of the hinge lower arms. The upper and lower cuffs include an outer relatively rigid layer of synthetic plastic material on an inner soft foam liner, and an elastic strap bridges the lateral edges of the cuffs wherein the upper cuff encircles the thigh above the knee, while the lower cuff encircles the leg shin below the knee joint.
Strap fasteners in the form of hook or loop patches such as available under the trademark Velcro are mounted on the cuffs for cooperation with Velcro material defined on the knee cage straps. Thus, the upper portion of the knee cage can be drawn firmly into engagement with the knee by the associated upper straps and the tension in the straps is maintained by affixing the crossed outer strap ends to the upper cuff. Likewise, the nonelastic straps attached to the lower region of the knee cage are crossed at the back of the leg and pulled tight for attachment of the strap outer ends to the lower cuff. In this manner the knee cage is firmly located upon the knee wherein the upper and lower cuffs can be considered to be "suspended" from the cage.
A de-rotator shin-engaging plate is, preferably, located intermediate the lower cuff and the knee cage and is strapped to the lower region of the brace to reduce rotation of the tibia.
The hinge located at each lateral portion of the knee cage is formed by a plurality of plates receiving the inner ends of the hinge arms therebetween. The plates include bosses into which threaded stop screws are received which are in alignment with the ends of the rack located between the arms' inner ends. By regulating the longitudinal position of the stop screws the end of the screws can be positioned as desired and will engage the rack ends in a positive abutment manner wherein the force of the rack is longitudinal to the screw length. A hinge constructed in accord with the invention is capable of accurately limiting and maintaining angular relationships between the arms mounted on a common body, and although relatively high forces may be imposed upon the stops, the use of the rack and the abutment of the rack with the threaded stop screws insures consistent adjustment and control of the range of pivotal motion of the hinge arms over indefinite duration.